1. Field of the Invention
The invention relates to compositions suitable for use in heat-generating reactions, and, more particularly, to improved compositions which are capable of undergoing exothermic reactions in the condensed state to form intermetallic products.
2. Description of the Prior Art
Mixtures of certain elemental metal and metalloid powders are known to be capable of reacting in a self-sustaining manner at high temperatures to form intermetallic products. Such heat-generating reactions generally proceed without the formation of a gaseous species, either as a product or intermediate or by boiling or decomposition of a reactant. Examples of condensed state compositions evidencing an exothermic reaction are given in Vol. 21, Combustion and Flame, pp. 77-89, 91-97 (1973). A number of compositions are disclosed, including boron and carbon mixtures with titanium and zirconium.
Sustainer and booster compositions which undergo heat-generating reactions are employed in, e.g., ordnance and pyrotechnic devices. A sustainer is a composition formulated without significant compromise toward sensitivity (ease of initiation). A booster is a composition having greater sensitivity, permitting its use as an intermediate step in initiation between a sustainer and a convenient first fire, such as an electrical initiator.
During condensed state reaction of a compacted mixture of heat-generating powders, heat transfer may be hampered by an overall increase in compact void fraction due to expansion of entrapped gases and vaporized impurities. This is detrimental in booster compositions, since empirical evidence shows that certainty of sustainer reaction is proportional to the heat transfer rate between the igniter and sustainer compositions. A reduction of heat transfer in sustainer compositions is also detrimental, since such reduction can lead to incomplete reaction.